An electronic device may include one or more circuit boards. A typical circuit board is a planar board that mechanically supports electronic components. The electronic components may comprise, for example, resistors, capacitors, switches, batteries, and other more complex integrated circuit components, i.e. microprocessors. The circuit board typically comprises a dielectric material, for example, a plastic material.
A simple circuit board may include conductive traces on its surface for connecting the electronic components to each other. As electronic circuitry has become more complex, multi-layer circuit boards with at least two electrically conductive trace layers sandwiched between dielectric layers have been developed. Typically, the different conductive trace layers of a multi-layer circuit board may be connected through vertically extending vias, which comprise conductive materials, for example, metal.
In certain applications, it may be desirable to interconnect two circuit boards arranged at a 90 degrees angle, each having electrically conductive pads on the major surfaces thereof. In other words, the edge surface of a first circuit board is mounted onto the major surface of the second circuit board. Moreover, this interconnection is typically accomplished using an interconnector component on the major surface of the second circuit board. Typically, the interconnector component physically couples the first and second circuit boards together and electrically couples the electrically conductive pads. The use of the interconnector component may increase the size of the assembled circuit boards. This may pose installation drawbacks in applications where space may be limited.
One approach to the above drawback is to interconnect circuit boards without using a separate interconnector component. For example, U.S. Pat. No. 6,345,989 to Mason et al. discloses a circuit board interconnector. The circuit board of Mason at al. includes conductive traces that extend outwardly beyond the edge surface of the circuit board, and contact pads provided thereon with a gap between the contact pads and the edge surface.
Another approach is disclosed in U.S. Patent Application Publication No. 2007/0107935 to Hash et al., also assigned to the assignee of the present application, Harris Corporation of Melbourne, Fla., the entire contents of which are incorporated by reference herein. Hash et al. discloses a method for fabricating contact pads within the edge surface of the first circuit board. The edge surface contact pads are coupled with the contact pads of the second circuit board. The method comprises drilling vias into each individual layer of the multi-layer circuit board, filling each via with an electrically conductive material (providing cylinders within the layer), and milling the layer to bisect the cylinders. One drawback of the Hash et al. method is the expense per unit for manufacturing may be high. Moreover, the vias for each of the layers need to be accurately aligned, adding a possible drawback to robust fabrication.